Cross-scale predictive dictionaries

Visual signals exhibit strong correlation across scales that is often modeled and exploited to enhance image processing algorithms [2], [28]. An important example of this idea is the multi-scale coding of images using the wavelet-tree model which provides a sparse as well as a predictive model for the occurrence of nonzero wavelet coefficients across scales [33]. Specifically, the wavelet tree model arranges the wavelet coefficients of an image onto a tree such that nodes on the tree correspond to the coefficients and each level corresponds to coefficients associated with a particular scale. Under such an organization, the dominant nonzero coefficients form a connected rooted sub-tree [5], i.e., children of a node with small wavelet coefficients are expected to take small values as well. The wavelet tree model is central to many compression [29], sensing [7], [9], and processing algorithms [5].